51. Community Ecology

A field contains 950 kg of plant material. How many kilograms of tertiary consumers could be supported?

Why does succession of communities occur?

What is the current view of biological communities?

Which of the following statements correctly describes conditions on a glacier moraine during the reign of pioneer species?

When equilibrium is reached on an island, __________.

What are two key factors in species richness equatorial–polar gradients?

What happens to the number of species in a community as the area of that community increases?

The potential evapotranspiration is determined by __________.

Which of the following is the definition of a pathogen?

What is a zoonotic pathogen?

The feeding relationships among the species in a community determine the community's a. secondary succession. b. ecological niche. c. species richness. d. trophic structure.

Based on the intermediate disturbance hypothesis, a community's species diversity is increased by a. frequent massive disturbance. b. stable conditions with no disturbance. c. moderate levels of disturbance. d. human intervention to eliminate disturbance.

According to the island equilibrium model, species richness would be greatest on an island that is a. large and remote. b. small and remote. c. large and close to a mainland. d. small and close to a mainland.

Pioneer species tend to have high                 and lower survivorship.

According to the generalized species-area curve, when habitat is reduced to 50% of its original size, approximately                    of the species once present there will be lost. a. 10%; b. 25%; c. 50%; d. 90%; e. it is impossible to estimate the percentage

Predators that are keystone species can maintain species diversity in a community if they a. competitively exclude other predators. b. prey on the community's dominant species. c. reduce the number of disruptions in the community. d. prey only on the least abundant species in the community.

Which of the following organisms is mismatched with its trophic level? a. algae—producer b. phytoplankton—primary consumer c. carnivorous fish larvae—secondary consumer d. eagle—tertiary or quaternary consumer

Food chains are sometimes short because a. only a single species of herbivore feeds on each plant species. b. local extinction of a species causes extinction of the other species in its food chain. c. most of the energy in a trophic level is lost as energy passes to the next higher level. d. most producers are inedible.

Which of the following best illustrates ecological succession? a. A mouse eats seeds, and an owl eats the mouse. b. Decomposition in soil releases nitrogen that plants can use. c. Grasses grow in a deserted field, followed by shrubs and then trees. d. Imported pheasants increase in numbers, while local quail disappear.

Which of the following could qualify as a top-down control on a grassland community? a. limitation of plant biomass by rainfall amount b. influence of temperature on competition among plants c. influence of soil nutrients on the abundance of grasses versus wildflowers d. effect of grazing intensity by bison on plant species diversity

What is a disturbance? Consider the role of fire in a forest. Compare the consequences of high-frequency versus low-frequency fire, and high severity versus low severity of fire.

The most plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is that a. tropical communities are younger. b. tropical regions generally have more available water and higher levels of solar radiation. c. higher temperatures cause more rapid speciation. d. diversity increases as evapotranspiration decreases.

Draw a vertical food chain (part of a food web) showing that sea urchins eat kelp and that sea otters eat sea urchins. Use this model to (1) show or explain how a trophic cascade works; and (2) offer an explanation for why otters are considered a keystone species.

Community 1 contains 100 individuals distributed among four species: 5A, 5B, 85C, and 5D. Community 2 contains 100 individuals distributed among three species: 30A, 40B, and 30C. Calculate the Shannon diversity (H) for each community. Which community is more diverse?

In Southeast Asia, there's an old saying: 'There is only one tiger to a hill.' In terms of energy flow in ecosystems, explain why big predatory animals such as tigers and sharks are relatively rare.

About a third of insect species measured are in decline, meaning that their populations are shrinking due to habitat destruction, pollution, and other factors. Predict how this change affects the bee pollination of crops such as apples and almonds.

Suppose that a two-acre lawn on your college's campus is allowed to undergo succession. Describe how species traits, species interactions, and the site's history might affect the community that develops.

There are fewer lions in Africa's Serengeti than there are zebras. This is principally because                   . a. zebras tend to drive off lions; b. lions compete directly with cheetahs, whereas zebras do not have any competitors; c. zebras have mutualists that increase their population, whereas lions do not; d. there is less energy available in zebras to support the lion population than there is in grass to support the zebras; e. zebras are a keystone species, whereas lions are not

A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods. Rather than measuring the entire 6000-hectare (ha) forest, the researchers sampled arthropod diversity by intensively collecting as many arthropods as they could in 12 plots that measured 20 m×20 m square. If 1 ha=10,000 m2,, how many hectares of forest did they sample in all? a. 20 m×20 m×12=4800 ha b. 4800 m2×10,000 m2/1 ha=48,000,000 ha c. 20 m×20 m=400 ha d. 4800 m^2 x 1ha/10,000 m^2 = 0.48 ha

SCIENTIFIC THINKING An ecologist studying plants in the desert performed the following experiment. She staked out two identical plots, which included a few sagebrush plants and numerous small, annual wildflowers. She found the same five wildflower species in roughly equal numbers on both plots. She then enclosed one of the plots with a fence to keep out kangaroo rats, the most common grain-­eaters of the area. After two years, to her surprise, four of the wildflower species were no longer present in the fenced plot, but one species had increased dramatically. The control plot had not changed. Using the principles of ecology, propose a hypothesis to explain her results. What additional evidence would support your hypothesis?

A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods. The graph below shows some of the data for the major arthropod groups collected. Notice that the scale on the y axis is logarithmic to make both small and large numbers legible on the same graph. For example, there are about 400 species of spiders, but only 40 species of bees. About how many arthropods were found in total? About what percentage of these were beetles?

"In a classic study, John Teal measured energy flow in a salt marsh ecosystem. The table below shows some of his results. a. What percentage of the energy in sunlight was converted into chemical energy and incorporated into plant biomass? What term describes this new biomass? b. What percentage of the energy in plant biomass was incorporated into the bodies of the primary consumers? What became of the rest of the energy (see Figure 37.16A)? c. How much energy is available for secondary consumers? Based on the efficiency of energy transfer by primary consumers, estimate how much energy will be available to tertiary consumers."

A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods.A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods. Use the data in the graph to analyze the following statements. Select True or False for each statement, then correct any false statements to make them true. T/F All taxa shown in the graph are insects. T/F All taxa shown in the graph have segmented bodies and limbs. T/F All taxa shown in the graph are terrestrial. T/F If the researchers had sampled for mollusks, they probably would have found almost as many species as they did for arthropods.

Lyme disease is caused by infections of the bacterium Borrelia burgdorferi (stained blue in inset, among red blood cells) which is transferred to humans via blood-sucking bites from the tick, Ixodes scapularis. Lyme disease can cause flu-like symptoms in the short term and more serious illnesses in the long term, if not treated. Why is Lyme disease on the rise in eastern North America? Researchers have measured a positive correlation between forest fragmentation and incidence of Lyme disease. According to the theory of island biogeography, how do you predict fragmentation will affect species richness?

Lyme disease is caused by infections of the bacterium Borrelia burgdorferi (stained blue in inset, among red blood cells) which is transferred to humans via blood-sucking bites from the tick, Ixodes scapularis. Lyme disease can cause flu-like symptoms in the short term and more serious illnesses in the long term, if not treated. Why is Lyme disease on the rise in eastern North America? White-footed mice occupy a broad ecological niche—they occur in most communities regardless of habitat quality. Many other species, like the opossum, are absent from low-quality forest fragments. Based on this information and the data in Question 12, propose a hypothesis to explain the observed relationship between increased forest fragmentation and increased incidence of Lyme disease.

A team of 102 scientists spent a year surveying a small area of the San Lorenzo rain forest in Panama to count the number of species of arthropods living there. After collecting 129,494 specimens—using nets, traps, shovels, tree-climbing harnesses, helium balloons, and other creative gear—it took the team eight years to sort and identify the arthropods. By comparing the number of arthropod species that were common among the 12 plots sampled, the researchers estimated that the total number of arthropods in the whole San Lorenzo forest is 25,000 species. To come up with this estimate, what's one assumption the researchers had to make about the forest?

Lyme disease is caused by infections of the bacterium Borrelia burgdorferi (stained blue in inset, among red blood cells) which is transferred to humans via blood-sucking bites from the tick, Ixodes scapularis. Lyme disease can cause flu-like symptoms in the short term and more serious illnesses in the long term, if not treated. Why is Lyme disease on the rise in eastern North America? A letter to the editor in a local newspaper asserts that 'we cannot afford to preserve natural forests, because we need to use these resources to help humans.' How could you respond to this comment in terms of Lyme disease?

The North American pronghorn looks and acts like the antelopes of Africa. But the pronghorn is the only survivor of a family of mammals restricted to North America. Propose a hypothesis to explain how these widely separated animals came to be so much alike.